May 15, 2017
Almost half (45.2%) of all US men tested with a swab of the penis in a nationwide sample were positive for at least 1 of 37 strains of human papillomavirus (HPV), reported researchers here at the American Urological Association (AUA) 2017 Annual Meeting.
The high prevalence of DNA-detected HPV on the surface of the penis was "surprising," said Mickey Daugherty, MD, a urologist at Syracuse University in New York. Some audience members at his oral presentation of the data at the AUA meeting were "very surprised" at the finding, he said.
The findings were also published in January in JAMA Oncology and were released in April by the Centers for Disease Control and Prevention (CDC) in a data bulletin.
Indeed, the findings are dramatic (and have made for attention-grabbing headlines).
But the full story, especially for clinicians, including oncologists, is a subtler tale, suggested Joel Palefsky, MD, professor of medicine, University of California San Francisco, who also made a HPV-related presentation at the meeting.
"Just because 45% of the male population has detectable HPV DNA doesn't mean that they have disease that needs to be treated," he told Medscape Medical News.
Dr Palefsky, who is past president of the International Papillomavirus Society, gave an example. A man can have a sexual encounter with a woman who is HPV-infected and end up with HPV on the surface of his penis. But the HPV can then go away because it is a case of what's known as carriage — and not infection. "A true infection occurs when the virus gets down to the basal cell layer," he commented.
For these reasons, the diagnosis of a true infection requires a minimum of two consecutive positive DNA results, said Dr Palefsky. In other words, you need to make sure the HPV has taken root and is not fleeting.
This distinction returns the story to Dr Daugherty and the above-mentioned nationwide sample with the surprising rate of HPV DNA detected on US penises.
That sample is the National Health and Nutrition Examination Survey (NHANES), an ongoing epidemiologic effort from the CDC that is unique in that it combines questionnaires and physical exams. For the first time, in 2013–2014, the NHANES investigators performed penile swabs on male survey participants in order to assess the presence of HPV.
"This is the first population-level data on HPV prevalence in asymptomatic men," observed Tim Byler, MD, who is one of Dr Daugherty's coauthors, is also from Syracuse University, and spoke with Medscape Medical News at the AUA meeting.
So, it's a landmark effort.
But it has a "weakness," said Dr Palefsky. "There was only one sample taken."
The HPV literature is "confused" by this lack of differentiation between one-time HPV testing and more thorough testing, he further said.
Whatever the exact percentage of penile HPV infections in the United States, infection with the virus is the most common sexually transmitted infection, by far, with herpes a distant second, said Dr Palefsky. "There is a lot of HPV out there," he commented.
Importantly, HPV is cleared by the body over time in most cases among both men and women, pointed out another presenter at the AUA meeting.
About 70% of HPV infections are cleared by the body's immune system in the first year and 90% are cleared by 2 years, said Landon Trost, MD, a male infertility and andrology specialist at the Mayo Clinic in Rochester, Minnesota.
However, once again, Dr Palefsky said this was a nuanced fact.
"I don't believe anybody clears the virus," he said. Instead, most people "control" the virus to the point that it becomes undetectable via commercially available tests. The virus may resurface in immunosuppressed individuals years later, as has been shown in people with HIV, he said.
Dr Daugherty also reported that the high-risk strains of HPV (16 and 18) were present in only 5.8% of men's penises in the most recent NHANES results. These strains are the primary drivers of HPV-related cancers, including penile cancers.
However, HPV infection in the penis rarely results in penile cancer. Only about 2000 penile cancer cases occur per year in the United States. Penile cancer is present at rate of about 2 per 100,000 men. Its incidence rate has been low and steady in the United States for years, said Dr Palefsky.
"The penis is not a particularly transformable organ," he said, referring to the development of cancer. The cervix is more transformable because of hormones, temperature, moisture, and other factors.
Nevertheless, with HPV so common in the penis, the question arises: How do you diagnose penile HPV infection? Should you be looking for penile HPV?
"The answer is no," said Dr Palefsky.
There is no US Food and Drug Administration–approved test. Penile swabs for HPV DNA have "unclear value," he said. These would include the swabs used by the NHANES investigators. "There is no clinical action that can be taken if you find out the person is HPV positive," he also commented.
"The best approach to dealing with HPV is to prevent the infection in the first place," Dr Palefsky said, referring to vaccination.